Plastisol binder composition for rocket propellants containing azide and hydrazine compounds



United States Patent ABSTRACT OF THE DISCLOSURE The invention is to aplastisol composition comprising a polymeric triaminoguanidinium azidebased source material, a high molecular weight hydrophilic polymercontaining functional anhydride groups and a liquid organic compoundhaving a carbon to nitrogen ratio of at least one and having at leasttwo groups. This plastisol has a reducing character, possesses a higherenergy than conventionally employed binders and serves to provideexcellent strength and structural characteristics in the fabricatedpropellant grain.

This invention relates to plastisol compositions and more particularlyis concerned with a novel plastisol having a reducing character which isparticularly suitable for use as a binder for solid propellants.

In the rocket and missile art, an ideal solid propellant composition isconsidered to be a fuel-oxidant mixture which not only is able to meetthe diverse requirements of formulation and fabrication but alsopossesses the requisite strength to retain a predetermined configurationunder flight and combustion conditions. Fuels and oxi dizers alonecannot on a practical basis be fabricated into a propellant grain havinggood strength and structural characteristics. To fabricate solidpropellants which meet the requirements for strength and configurationstability, binder materials must be employed. Conventionally, plastisolbinders such as solid polymeric nitrocellulose or polyvinyl chlorideplasticized with relatively non-volatile liquid oxidants such asnitroglycerine, triethylene glycol dinitrate or trimethylolethanetrinitrate are employed. Although the resultant propellant compositionspossess good strength and structural characteristics, the use of theseconventional binders lowers the impulse over that which would beachieved by use of the fueloxidizer alone.

Now, unexpectedly a novel binder composition for solid propellants hasbeen found which possesses a higher energy than the conventionallyemployed binders as well as serves to provide excellent strength andstructural characteristics in the fabricated propellant grain.

It is a principal object of the present invention to provide a novelplastisol binder for propellants employing non-oxidizing plasticizers;

It is another object of the present invention to provide a high energybinder for solid propellants which has desirable high nitrogen to carbonand hydrogen to carbon ratios resulting in lower molecular weightexhaust gases and hence a higher l It is a further object of the presentinvention to provide a plastisol binder which imparts good tensilestrengths to cured compositions of fuel, oxidizer and binder as well asgives uncured compositions having viscosities which permit the necessaryoperations of mixing and casting during propellant grain fabrication.

It is another object of the present invention to provide "ice a novelbinder composition which exhibits a high elongation thus providing aflexibility which leads to good characteristics during thermal cyclingand resistance to cracks on ignition.

It is also an object of the present invention to provide a novelplastisol binder composition the physical properties and energy contentsof which are such that a minimal decrease in thrust results when thebinder is incorporated into a propellant composition.

These and other objects and advantages readily will become apparent fromthe detailed description presented hereinafter.

The present novel plastisol composition comprises l) a polymerictriaminoguanidinium azide based source material, (2) a high molecularweight hydrophilic polymer containing functional anhydride groups and(3) a liquid organic compound having a carbon to nitrogen ratio of atleast one and having at least two groups as a fluidizer for thepolymeric triaminoguanidinium azide based source material. (Hereinafter,the term polytriaminoguanidinium will be used as a designation for thepolymeric triaminoguanidinium based materials.)

More particularly, the plastisol composition of the present inventioncomprises from about 20 to about 90 weight percent ofpolytriaminoguanidinium azide or a modified polytriaminoguanidiniumazide resulting from the pyrolysis of triaminoguanidinium azide in thepresence of either cyanamide or malononitrile, or mixtures ofpolytriaminoguanidinium azide and such modified polytriaminoguanidiniumazide materials, from about 5 to about weight percent of either a methylvinyl ether-maleic anhydride copolymer, an ethylene-maleic anhydridecopolymer or mixtures thereof and from about 5 to weight percentethylene dihydrazine, hydrazine, monomethyl hydrazine, monoethylhydrazine, sym.dimethyl hydrazine and ethyl ene diamine. Of thesefiuidizers, hydrazine, monomethyl hydrazine, monoethyl hydrazine,sym.-dmiethyl hydrazine and ethylene diamine are apparently lessstrongly hydro gen bonded than is ethylene dihydrazine. Therefore, in agiven composition, within the concentration range set forth herein, toproduce the same degree of fluidity quantities of the less readilyhydrogen bonded fluidizers used are only about half of ethylenedihydrazine.

Preferably the present novel composition comprises from about 50 toabout weight percent of polytriaminoguanidinium azide or a cyanamide ormolononitrile modified polytriaminoguanidinium azide, about 15 percentof a high viscosity methyl vinyl ether-maleic anhydride copolymer or ahigh viscosity ethylene-maleic anhydride copolymer and from about 10 toabout 35 weight percent ethylene dihydrazine.

The modified polytriaminoguanidinium azide materials suitable for use inthe present invention can be prepared by pyrolyzing triaminoguanidiniumazide with ether malononitrile or cyanamide. Ordinarily in the actualpreparation of these modified polytriaminoguanidinium azide materials,triaminoguanidinium azide and from about 2 to about 20 weight percent,based on the weight of triaminoguanidinium azide, of malononitrile orcyanamide are reacted in a slurry reactor in the presence of an inertcarrier, eg a paraffinic hydrocarbon, for a period of from about 2 toabout 10 minutes at a temperature of from about to about C. Themalononitrile modified triaminoguanidinium azide or cyanamide modifiedpolytriaminoguanidinium azide product is recovered almost quantitativelyas a solid ranging in consistency from a tatfy-like material to a coarseor fine powder. The

3 product form as well as N/C ratio can be predetermined by the reactantproportion and reaction conditions employed.

In using the plastisol composition of the present invenconventionalpractice, fuel-rich propellant grains are used in such hybrids to avoidignition problems in on-olf operation because conventional hybridbinders are not hypergolic with oxidizers. Ethylene dihydrazine, forextion as a binder for a solid rocket propellant system, the 5 ample, ishypergolic with N 0 ClF and the like oxidizers binder is mixed with thefuel, oxidizer and other additives thereby providing the additionaladvantage that the presthat may be employed. The components are blended,ent binder system can be used satisfactorily in on-otf solid poured, andcast, pressed, or extruded into a predepropellant systems. terminedpropellant grain configuration. The grain is The following examples willserve to further illustrate cured and subsequently treated in aconventional manner. the present invention but are not meant to limit itthereto. The binder will be used in an amount of from about 10 toExample 1.-About parts by weight of a methyl vinyl QbOLllI 60 weightpercent Of the total propellant grain, d6- ether-maleic anhydride copolymer (Gantrez, Ali-#169) p f P energy h Strength requll'emehts 0f wasadded to a mixture of about 65 parts by weight polygrain as discussedhere nbefore. triaminoguanidinium azide and parts by weight ethylene hPresent novel hind?! COmIfOSItIOIl (fall he used In 15 dihydrazine. Tothe resulting plastisol composition was fahrlcatlhg P p -fl graljlshavlhg oxfdlzefs and fuels added about 300 parts by weight of 20 meshglass beads Selected iron} Wide Vanety of mammals p y In which served asa simulated solid fuel and oxidizer. The such compositions. resultingmixture was blended, cast into standard micro- FOY h Pl OXldlZefS Suchas amhtohlun} Perchlorate, tensile mold forms and cured at about 65 C.under a coated nitro1iium Perchlorate, aihmohlllm hltrate, F h 20 drynitrogen atmosphere. Determination of the tensile hydrallhfihltrofofhlate, y hf p f llthlum strength and elongation after 24 hourscure indicated Perchlorate, y f' h tflhltramlhe Y the strength of thecured simulated propellant grain to be tetramethylehe tetl'ahltfamlhe hthh all 63 pounds per square inch. The grain exhibited an elon- Canblended with the Present hovel blhderslfhltarly gation of about 26percent. Examples which were cured p r i l m l f l such a al min m n hm, for 42 hours exhibited a tensile strength of about 135 light metalhydrides such as lithium hydride, aluminum pounds square inch i 30percent elongatiom y f y h y hthium ahllhmulh hychlde A number oftensile test specimens formulated from ofgalllc HItTOgFKI-hYdIOgBII h fihavlhg hlgh the same composition as described directly hereinbeforeratios such as S-ammotetrazole, diaminotetrazene, tr1ami were Cast intothe i1 molds and cumd f noguflhldlhlufn azide hy r z1ne azi de doubleSalt, 30 periods of from about 1 to about 10 days at temperal l h allde.Salts Such dlamlho' and fnonoammo" tures ranging from about roomtemperature to about 70 guahldlhlhlh azlde and the llke can also beIncorporated C. The results of this study indicated that a temperatureInto the h of at least about 45 C. is required to achieve curing Thercduclhg fuel yp h 0f the Present f within from about 1 to about 5 days.At temperatures tion are uniquely adapted for use in the sol d fuel secton about 55 to about 65 C. a satisfactory cure resulted of y yp rocketsWhere the oXldllel 1S Stored within from about 1 t oabout 5 days. Attemperatures separately from the fuel and controllably -fed onto the abv 70 C. gassing occurred. In the preparation of a combustion surface ofthe fuel. The highly desirable startpropellant i thi ould lead toundesirable voids i stop feature of this type of rocket enables theomission th cured product, p of oxidizers from the solid fuelcomposition as well as a Example 2.Following the same formulationprocehypergolic reaction between oxidizer and fuel material. In duresdescribed in Example 1 a number of binders were TABLE I FormulationBinder composition, percent by weight composition, Tensile strrength ofcured formulations percent by weight Polytri- Maximum tensile,Elongation at Ultimate elongaaminoguap.s.i. maximum tensile, tion,percent nidinium Polymer Cure percent; Run azide source temper- No.material eture,

Ethylene 0 Cure time at 60 0., days dihydra- Binder Filler Cyanemidezone Methyl modified vinyl polytrietheraminoguamaleic 1 2 5 6 1 2 5 6 12 5 6 nidinium anhydride azide 1 25 60 15 33 67 60 25 24 28 30 so 27 3050 35 15 33 67 60 25 25 2s so 85 64 65 20 15 33 67 60 24 32 4s 22 90 683a 65 20 15 25 75 60 27 4s 25 53 26 42 7o 15 15 30 70 60 2s 45 2s 39 2222 75 1o 15 33 67 6O 29 57 9 17 167 22 7o 15 15 46.5 44.6 89 64 21 15 3a67 24.1 32.4 21.7 Ethylene maleic anhydride copolymer Polytri- Methylaininoguavinyl nidine etherazide maleic anhydride :iiitl oxidizer.

1 N/C ratio 5. Prepared by pyi'olyziug triaiiiinoguaiiidinium azido with20 percent by weight of cyanainide. Glass bcads-sin1ulated solid fuelprepared and those cured alone or after blending with glass beads (100US. Standard Sieve). The resulting compositions were cast and cured fora predetermined period of time at either about 50 or about 60 C. Tensilestrength and elongation of the resulting cured binders or grains weredetermined.

The composition data and strength characteristics of the resulting curedproducts are summarized in Table 1.

Example 3.The binder compositions described in Examples 1 and 2, uponblending with particulate ammonium nitrate and particulate aluminum, forexample, at binderfuel oxidizer ratios corresponding to those set forthin the examples and providing substantially fuel-oxidizer balancedgrains, when cast into grains and cured as set forth herein providesubstantially void-free, elastomeric solid propellant grains.

This grain burns smoothly with high impulse and good efiiciency.

Plastisols of the same general characteristics can be prepared using amalononitrile modified polytriaminoguanidinium azide in conjunction withthe polymer and fluidizer for the polytriaminoguanidine azide set forthhereinbefore.

In a manner similar to that described for the preceding examples,plastisols in accordance with th present invention and suitable for useas propellant binders can be prepared using hydrazine, monomethylhydrazine, monoethyl hydrazine, sym.-dimethyl hydrazine and ethylenediamine as a solubilizer or fiuidizer for the polytriaminoguanidiniumazide based component. Likewise other high molecular weight hydrophilicpolymers containing anhydride functional groups can be utilized as thereinforcing member for the polytriaminoguanidinium azide basedcomponent.

Various modifications can be made in the present invention withoutdeparting from the spirit or scope thereof for it is understood that welimit ourselves only as defined in the appended claims.

We claim:

1. A plastisol composition which comprises (a) from about 20 to about 90weight percent of a polytriaminoguanidinium azide based source material,

(b) from about 5 to about 20 weight percent of a high molecular weighthydrophilic polymer containing functional anhydride groups which polymeris selected from the group consisting of methyl vinyl ether-malei-canhydride copolymers, ethylene-maleic anhydride copolymers or mixturesthereof, and

(c) from about 5 to about weight percent of a liquid organic compoundhaving a carbon to nitrogen ratio of at least one and having at leasttwo liquid organic compound is ethylene dihydrazine.

4. The composition as defined in claim 2 having from about 50 to aboutweight percent of said polytriaminoguanidinium azide source material,about 15 weight percent of said methyl vinyl ether-maleic anhydridecopolymer, ethylene-maleic anhydride copolymer or mixtures thereof andfrom about 10 to about 35 weight percent ethylene dihydrazine.

References Cited UNITED STATES PATENTS 3,206,341 9/1965 Reynaud et al.149-36 X 3,268,376 8/1966 Haldeman et al. 14936 X 3,288,660 11/1966Niles et al. l49----36 BENJAMIN R. PADGETT, Primary Examiner.

